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Why can't helicopters or Zeppelins drop fire-fighting material on burning buildings?
There have been a number of tragic cases where tall buildings have caught fire for various reasons, and fire-fighters on the ground appear to have been unable to reach the upper stories with fire hoses.
As a child watching 9/11 unfold, I remember wondering why, given that helicopters were being used to film the events, it would not be possible for helicopters, or perhaps airships, to be loaded with water or foam and fly over burning buildings, dousing them.
Of course, in retrospect, I understand that the World Trade Centre buildings were so vast and the fire (and structural damage) so enormous that this would have made little practical difference.  But what about cases of relatively smaller tower blocks, such as the recent tragedy in the Grenfell block in London?
I assume that there must be some practical reason why this cannot be done, on the grounds that this is something which presumably would be being done if it were possible.
Is it simply that the weight of a large amount of water would be too heavy for a helicopter to carry?  Would this apply to airships?

Mostly because the fire is inside the building, and dumping water on the outside of the building and roof wouldn't stop the burning on the inside.

One thing is heat from fire will create strong turbulent column of rising air. Helicopter or any aircraft does not like anything turbulent. To drop anything on precise location needs specific positioning which is not easy to do here. Weight is not a problem as you sometime see helicopter drop water to fight forest fire.

@RonBeyer In the case of the Grenfell tower, the problem seems to be that the fire was NOT just inside the building, but travelled up the exterior cladding. This meant that the usual fire precautions designed to prevent fires spreading between flats failed. Dumping water on the exterior cladding might have helped in this case.

@vasin1987 Is there a reason you didn't post an answer? That comment shows that you understand some of the fundamentals of the challenges proposed in the question.

@KorvinStarmast just my pure laziness :)

One (well, this one) wonders if something akin to the infamous "puff the magic dragon" could make repeated slow flybys of a burning building, with its internals stuffed with foam and hoses rather than guns n' ammo. They are already proven at flying above and around areas from which "materials possibly injurious to the wellbeing of craft and crew" may be emitted.

@GrimmTheOpiner  agreed, about six AC-130 water bombers with fire nozzle where the howitzer goes, and ability to scoop water while flying, could've saved WTC.  But while we're at it, an H-4 Hercules with an integral wet-dock containing a DSRV could've saved the Kursk crew.  The difficulty is in the probability and practicality of having such an exotic single-purpose bird exist, and be in exactly the right place at exactly the right time.  Maybe if they had FTL...

@Harper exactly right. Might be conceivable if the payload could be rapidly exchanged: cannon out, water cannon in.

First, they have been used, like in case of the Federation tower fire in Moscow on 2012. The image below shows a Kamov Ka-32A11BC being used to fight fire in that case.

Helicopter fighting Federation Tower fire in Moscow; image from dailymail.co.uk
According to a news article

The Ka-32A11BC proved its fire-fighting credentials in April 2012, when a blaze engulfed ... the 67th floor at the Federation Tower in Moscow, Russia, more than 270 meters above ground level. ... the fire was only contained after two Ka-32As belonging to the Russian Emergencies Ministry were called into action and ferried in water from the nearby Moscow River.

However, there are multiple issues in using helicopters for urban firefighting.

Helicopters are all but powerless is case of fires breaking out over the lower floors. Even in the above case, the helicopters were useful only as the fire broke out in the top floor of the (then under construction) skyscraper. For lower floors, the helicopter would have to carry the spraying equipment in the fuselage, which would make the useful payload impractical. Airships are all but useless in this case, while even helicopters would have difficulty getting through the buildings.
Firefighting using helicopters is not a precision business as it would be difficult to position the helicopters directly overhead due to the intense heat and the turbulence produced. For safety, the helicopters have to fly higher, which reduces efficiency due to winds.
Aerial firefighting is a costly business. As LA times puts it:

It costs up to \$14,000 a day to keep an air tanker on call and as much as \$4,200 per hour to put it in the air. Heavy-duty helicopters, the workhorses of aerial firefighting, can cost \$32,000 a day on standby, plus \$6,300 per hour of flight time.

and this in the US where the need to put out forest fires is all but certain.  Major fires in skyscrapers are infrequent and too scattered around the world to justify the expense of keeping a helicopter on standby in any given city.
The crew have to trained for this- firefighting is a dangerous business:

But unpredictable atmospheric conditions make flying over wildfires difficult and dangerous. Thirty-seven firefighters have died in aerial firefighting accidents in the last decade.

Urban environment with high rise buildings and power lines pose a separate set of challenges.
Water and firefighting slurry supplies have to made available- this is important in cases where for example, the rivers are seasonal. Not only is the normally used firefighting slurry costly, it is also not environment friendly.

... the slurry, which is rich in nitrogen, can harm fish, wildlife and watersheds, despite agency guidelines to prevent drops onto vulnerable areas.
Aerial firefighting is expensive. Tankers cost upwards of \$6,000 per hour to operate. The slurry itself averages about \$2 per gallon, and the Forest Service used almost 9 million gallons of it last year.

Airships have the same issues, and some more (payload and speed/maneuverability come into mind).

Just out of curiousity, why are standby costs so high? The figures quoted equal 3-5 hours of actual flight time just to stand by for the day.  Are they sitting on the tarmac idling and burning fuel for that period?  Does it cost a lot to pay people to just sit there?  Or is this just what they charge because they could have averaged that much time in the air had they not been on standby?

@Michael Note that the article quotes the cost to keep the aircraft 'on call'- practically ready to fly. In that case, the aircraft and crew must be flight worthy and ready; while the aircraft may or may not be fueled, it will be in a short notice- you're going to pay for the fuel service. It is basically like keeping the taxi waiting the whole day- you're keeping the aircraft that could've been used somewhere else by paying for it. Add to this the expenses for parking and ground support/handling equipment, you get the figure.

Also note that winds between tall high rises can be pretty extreme, fire or no fire. That's the main reason why airships don't currently dock with the Empire State Building as originally intended by its designers.

Couldn't we just build a very long fire hose, attach it to the helicopter, and then use the helicopter to point the hose at the fire? That would eliminate the need for the helicopter itself to carry the water internally?

@mickburkejnr you still need a disconnect on the tow line in case the bag gets tangled. A foolproof remote disconnect on a firefighting hose+electricity for the pump isn't trivial to design. The pump in the bag is also going to need to be substantial to be useful in firefighting.

@ratchetfreak I see. But what if the pump was to be placed on the ground? I'd reason you could, in theory anyway, mount a powerful enough pump to blast the water up through the hose? However, I would then reason the force the water would apply to the helicopter could potentially make it dangerous. Plus if the helicopter had to drop the hose, well I wouldn't want to be under it!

Interestingly, it looks like much of the water is going to miss the building in that photo, adding credence to the "it's hard to drop it accurately" argument.  Of course I expect a lot of that water to lose horizontal velocity due to air resistance, but it's still missed the middle of the building.

@mickburkejnr: The weight of the water in the hose will exceed the capability of the pump before you get high enough to be useful.

Fire creates heat, which in turn creates turbulence. While soaring enthusiasts welcome this as thermals, lighter-than-air captains dread such turbulence as their worst enemy. When the airship enters such a warm updraft, first the nose is lifted, and then the whole ship. At the same time, the airship starts to drop within that hot, rising air column, because now the  density of the outside air is reduced, reducing buoyancy. The ship will be tossed around and be very hard to control.
Dropping a large load at the same time makes matters worse. Now the ship has excessive lift and will accelerate upwards like a cork in water. If that upward movement cannot be stopped before the bounce height of the ship is reached, the gas bags will burst.
No, airships are completely unusable to fight fires.
Helicopters, on the other hand, make excellent precision firefighters. They can carry a limited load but place this with much higher precision than airplanes. Airplanes have an advantage in cost per ton of water and when the source of that water is some distance away.

Kamov helicopter dropping water (picture source)
In all cases, water would only be dropped from above, like rain, and buildings are designed to prevent rain from entering. Therefore, unless the roof structure is ablaze, this water would not reach the burning structure. With current technology, fires on higher floors of tall buildings can only be extinguished with a pre-installed sprinkler system or firefighters using water from pre-installed standpipes and hoses. Optimistic scenarios of helicopters shooting jets of water horizontally into a burning high-rise building have not materialized because the reaction force from shooting that jet of water would make the helicopter hard to control.

But note that helicopters can only drop water on the top of things. If a high-rise building is on fire, you almost certainly want to throw water at the side of it, which conventional firefighting helicopters can't do.

Early example of airship + updraft = disaster: USS Shenandoah

@DavidRicherby: In that, they are not much different to airplanes. They are not ideal for urban firefighting, but still better than airplanes.

Optimistic scenarios of helicopters shooting jets of water horizontally into a burning high-rise building have not materialized because the reaction force from shooting that jet of water would make the helicopter hard to control. AH64 pilots are pretty darned skilled with an anti-tank cannon though.

The most extensive use of helicopters for firefighting (and sealing a reactor) was Chernobyl. The Helicopters of Chernobyl In fact, nothing but a helicopter could possibly have performed the partial sealing of the exposed reactor, preventing a far worse release of radiation.
Sadly, the crews of those helicopters who responded immediately, died from radiation exposure not long after the initial disaster. The very radioactive helicopters were quarantined in a field for decades, until they were eventually destroyed to stop looting of parts.
Large airships... are just too vulnerable to extreme weather to be considered a reliable tool. While everyone remembers the fire of the Hindenburg, the only non wartime loss of an airship to a hydrogen fire, few remember the large dirigibles lost to storms: three notable examples are the USS Akron, USS Macon, and the British R101.

Helicopter firefighters do exist, and are used here in Australia for extinguishing bushfires. Elvis is here on a regular basis.

Bushfires just require to plonk a load of water on top of the burning area (just, as in doing a heroic job flying above a roaring fire) - spraying a water jet sideways from a heli would be more complicated but could probably be done, the dynamics would be analogous to those of a cannon on an attack helicopter. Airships might work yeah, the helium filled ones, if only they wouldn't blow away.

Image source
It probably boils down to a question of economics. This document lists the number of fires in tall buildings, and mentions that built-in fire suppression systems are effective. The Twin Towers was a highly visible event, but how many tall building fires are there per year in NY City, and would that justify having a highly specialised team of helicopters availabe, with the pumping equipment and amount of water on board to squirt sideways into mid building?
Helicopters don't have much speed and range and each big city with skyscrapers would have to maintain a fleet. There are 12 fires in tall buildings listed for New York City in the last 100 years in Wikipedia. It would be conceivable to seek cooperation with the Army to use attack helicopters and exchange cannon & ammunition for a water cannon & water payload - the highly trained expert pilots would do a grand job at this.

Whoa - according to this site, during the seventeen year period ending in 2002, 1600 civilians died and over 20,000 were injured in the approximate 385,000 high-rise building fires in the United States, excluding the MGM Grand Hotel and the Las Vegas Hilton fires in the early 80’s, and the World Trade Center on September 11, 2001.

Yes. Not disputing that. Firefighting is not a federal institute though.

Here are some statistics about high-rise fires in the USA.  The linked PDF has even more statistics, including:  the majority of high-rise fires start on the sixth floor or below;  fires in high-rise buildings are less likely to spread than fires in shorter buildings (due to having more suppression systems);  and seven out of ten of the deadliest high-rise fires in history started on the third floor or below. ...

In other words, very few high-rise fires are sufficiently high and sufficiently large that the ability to douse the fire from outside the building would be useful.  It's just that those that do spread to this point are the highly visible ones:  World Trade Center, Grenfell Tower, Address Hotel, One Meridian Plaza, etc.

Special airplanes and specially equipped helicopters ARE used to fight fires, mainly forest fires.
In parts of Europe, where I live, the name "Canadair" was synonym with the special firefighting planes, such as Canadair CL-215 and Canadair CL-415. Through my youth I was convinced that Canadair manufactures only firefighting planes, and only later I found out that they make passenger planes as well.
So the answer to that part is, they are used.
As to why they are (mostly) not used in urban environments, the answer is, there are better ways to prevent and fight fires in urban environments, so the need for a firefighting aircraft in urban areas is very infrequent. In properly maintained urban buildings you have fire alarms, sprinklers, and good access for the fire engines - while in the remote forests you have no such things.
Forest fires in southern Europe are quite regular and predictable occasion (due to tourists/visitors, sparks from the railways, etc.) so you can be sure that the fleet of firefighting aircraft in any country will be engaged for large part of the summer (and when not in use, they will be sent to help to their neighboring countries to help).
As people already explained, maintenance of these aircraft is costly and you cannot expect them to be sitting ready on the tarmac in London (for example) for 10 years without any engagement, until a fire breaks out in the building that was refurbished with flammable materials in what it seems now a criminal negligence. They also need time to be loaded with water (and perhaps chemicals, depending on the nature of the fire). When fighting fires in the wild (forests) they are never used alone (or even as first response), but always in combination with firefighters on the ground, if the terrain is difficult to access.
So, sadly, while a fully loaded Canadair CL-415 sitting on the tarmac with pilots ready for action 24/7 would perhaps help in Grenfell tower fire, having such aircraft ready 24/7 in urban environments simply does not pay off. And if it would not have been ready 24/7 it could not make any difference, since with Grenfell, the building was engulfed with flames within half an hour, if I remember correctly.
Of course, the issue of flying low in the city during the night over the fire also poses far greater risk than flying over a remote burning forest with accurately mapped topography (elevation).

First, the fire is inside the building, and dumping water on the outside of the building and roof wouldn't help.
Second, the upper part of the building being burned is very likely to fall down. The pulling of fire-fighting material may make it worse.

Agreed, in the case of Twin Towers the fire was not on the top floors and would have required sideways squirting of the extinguishing material. However, in case of Grenfell tower in Britain, just dumping water would have helped.

@Koyovis The fire at Grenfell Tower began on (iirc) the fourth floor and spread upwards. I don't see how dumping water from the top would have helped any more than it would have on the Twin Towers.

Was it established that the cause of the Grenfeel Tower fire was the external cladding?

@Koyovis no, the cause was a faulty kitchen appliance. The spreading of the fire may or may not have been (in part or entirely) due to the external cladding.

Oh right-o. I don't claim to be a fire-fighting expert.


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Why do airliners park with the nose facing the terminal?
A few other questions have touched on why we don't board airliners from the front and back at the same time. My question is why is it that we choose to board at the front, rather than park the aircraft facing away from the terminal? This question shows that parking backward seems to be unusual. Why is this design not adopted widely?
I have two guesses:

Is it because of the jet blast? But this can be solved by towing the aircraft away from the terminal before using the jet engines.
Because it is difficult to attach the jet bridge without hitting the tail?

@user3528438 About the jet engines, I think that can be addressed by having the plane towed far enough from the terminal before applying thrust.

@user3528438 And about the jetway, what if we connected the bridge to the rear door?

You propose an interesting point. You might have given the best reason for not doing this in your question. Attaching a ground tug to the aircraft for towing or pushback takes time and personnel. Why would an airport or airline spend that time twice when one of the times the aircraft can move perfectly well under its own power? And, a moving aircraft uses a lot less thrust to keep moving than a stationary aircraft uses to get moving.

As far as loading from both the front and the back...many countries operate just that way. When doing this, it always involves some or all of the passengers walking out to the aircraft, right on the apron/ramp. Then, walking up a set of portable stairs. Sometimes, that means taking a bus out to the plane that is parked far away from the terminal. That is how we did it here in the U.S. back in the 40s, 50s, & 60s. I think the American public is now too used to being protected from the elements (rain, snow, heat, cold, etc.) to go back to that.

Finally, how do you reasonably and economically design (retrofit) a transom or gangway that takes into consideration the various designs of tail empennages for different airplanes? There is a lot less difference in the shape and position of the doors in the front than the ones in the rear. You can ensure more consistency, compatibility, and mate-ability with most planes by attaching to a front door regardless of plane size or height.

The passengers want to get out ASAP. Turning round takes time.

Would it be too snarky to answer this with, "Because parallel parking a jet is just too much effort" ?

The old satellite concourses at LAX used to have planes park sideways with respect to the terminal walls, but once they were renovated into piers in the early 80s, they were changed to park forwards.

@DeanF. There are still plenty of large airports where that's common. Last time I had a stop in Beijing International (PEK) this is how we moved to our next leg. Ever since I've realized just how luxurious many 'western' airports are.

@Mast - Abu Dabi, Doha, Johannesburg, Manila, and Sri Lanka are all that way for their domestic flights. And, they are not exactly small airports. But, I would not call them large either compared to Heathrow, Ohare, and Hartsfield-Jackson.

While I applaud the novel idea, it would be incredibly difficult to do this! And then everyone would say "Why don't you do it the much easier and better way?"

Parking nose-to-terminal allows you to start the engines at the gate without jetblasting the terminal.  That way, if you find out upon engine start that there's an issue which requires sending the plane for maintenance and using a different plane for the flight, you can simply reconnect the jetway and deplane the passengers.  If you parked tail-to-terminal, necessitating pre-engine-start towing, you would have to push the aircraft back into the gate before reconnecting the jetway and deplaning, taking extra time.

To park a passenger plane with its tail towards the terminal has several disadvantages:

it would require a pushback tractor (plus personnel) to do that. Thrust reversers in general are not meant for making the plane go backwards. If it was possible for the plane to go autonomously backwards, it would be extremely = too risky.
you would also need the pushback tracktor for leaving the gate, you couldn't use engines because of the jetblast hitting the terminal
you could not use the APU because it would scorch the terminal
the horizontal tail of some planes might have clearance issues with the jet bridge.
last but maybe not least: the upper class travelers. They sit at the front for a reason: they get on and off the plane first. Yes, the business and first class could be moved to the back. Now, I don't know if riding closer to the cockpit rather than the arse of the plane has some intrinsic value, but at least it is usually noisier at the back.
So customer satisfaction might take a hit there.

So: twice the hassle with pushback + other issues, with no benefits whatsoever.

As always, there are exceptions, like London City, for example.

These are cases where the airport is not suitable for the planes operating there. It's kinda funny how a plane gets shorter when you park it differently...

In a few weeks I'll be flying from FRA to LCY in an E190. I'll keep you posted as to whether the plane's length changes upon arrival. ;-)

All good answers, jpe.  I would add that parking facing towards the terminal gets the impatient passengers off the plane faster.  Taking the time to back-in might push this already frazzled group over the edge.

@Jim And first class gets to (inefficiently) board and leave first.

@Schwern I thought of that too, and since you brought it up too, I added it into the answer. Moving the upper classes to the back might not be as simple as thought at first...

The rear of the aircraft is definitely noisier because you get the sound of the jetwash. The wing exit row is about the limit between the "relatively quiet" and "noticeably loud" parts of the aircraft, which is also why "economy plus" is located forward of the wing.

@LawnmowerMan related point - the front of the aircraft is "prettier" too, with observation windows, its nicer to look at the front and not the rear.

The downside of sitting at the front is that you are more likely to get killed in a crash. time.com: This Is the Safest Place to Sit on a Plane

Parking nose in requires that you back out, though.

@GeorgPatscheider I notice when I’m sat in first/business that I feel the plane pitching more compared to being sat directly over the CoG or aerodynamic centre where the ride is less... anxiety-inducing. I’m surprised airlines haven’t added a different class section to the middle of the plane and charged more for a smoother ride...

@Dai SHHHHH!!! There are already enough "premium" seats and many airlines charge a premium for exit row seating (since there's more leg room). Don't give them any more ideas to jack up prices of random other seats!

@FreeMan The trend seems to be towards  having to pay for any seat if you want to pick it before check in...

@arp: Yes, but you can at least taxi in under your own power that way.  If you parked tail-to-terminal, you'd need a tug for both the taxi in (since most aircraft aren't designed to use their thrust reversers to back up, airport authorities tend to frown on drifting large jetliners across the ramp, and doing the airplane equivalent of a handbrake turn tends to be rather hard on the aircraft) and the taxi out (since jet blast would do bad things to the side of the terminal).

I worked at an airport for 3 years.  We're under a very strict time table when an airplane lands.  An aircraft arriving and departing is called a "turn" and our turn time is roughly 15-30 minutes depending on type of aircraft.  Every moment counts.  Even a 1 minute delay will get people from corporate screaming at my manager for answers.  My manager in turn, would then scream at us.
Parking an aircraft so it's tail faced the building would be a massive increase to our turn time.  It would take a lot more trouble to take a push back up to the awaiting aircraft, hook it up, tow it back into position, then wait for engines to shut down and APU/Ground Power to come on, than it is to just have it roll up nose first and push back after loading it.
Furthermore, the jetbridge would have to manuever around the wings of the aircraft to get to the door, most bridges are too short for that so it's unfeasable, unless they rebuilt like ALL the jetbridges or used a staircase truck (which eats at turn time.)
The big one is safety.  The engines would be pointing their jetblast where the ramp agents come out of the building to do their work.  On most turns, the engines turn off and the APU or Ground Power is used.  But sometimes the APU is dead or some maintenance requires running engines.  We can't do that at the gate if the airplane is facing the building ass-first and finding a safe place to do such a thing may be incredibly difficult and inconveinent, or they can simply park at the gate nose first.

Well, the jet bridge would presumably connect to the last door instead of the first, so it would only navigate around the tail. It would still be harder than not having to navigate around anything though.

There are certainly airports where aircraft do face away from the terminal.
One example is London City, where aircraft use their own power to turn themselves round upon arrival. Also, low cost airlines might do this to speed up turn around time - I've seen Easyjet aircraft turn themselves round at Tenerife, although I can't remember if they did this on arrival or departure. Low cost airlines are also more likely to use both front and back doors to speed up disembarking and embarking of the aircraft.
To resolve the issue of jetblast and the terminal in these cases, there is an additional concrete barrier between the aircraft parking and the terminal. This works where the passengers walk (or get a bus) to the aircraft.
As has been mentioned, this does not work where airlines use a airbridge, nor for full service airlines who generally like to use an airbridge, in which case the airbridge(s) have to link to doors on the terminal side of the wings.

Does Dulles still use those AT-AT things?  I know they were capable of hooking up to either the front or rear doors.  Granted they came with a whole host of other problems, but it seemed like a good idea at the time...

@DarrelHoffman I saw them there I think 3 years ago, but they're apparently only used occasionally now, acc. to https://en.wikipedia.org/wiki/Mobile_lounge

@DarrelHoffman Oh, man. AT-ATs would be much cooler. United, ANA, and Virgin Atlantic should use those for their Star Wars livery jets. And Air New Zealand should get siege towers to board their Hobbit-themed jets.

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How can a person receive an expired life vest?
I wonder if passengers could receive an expired life vest because who else would they give to.

Welcome to Stack Exchange. Are you asking how you can get an expired life vest because you would like to own one? From the title, I thought you were asking how passengers could be mistakenly given expired life vests to use in emergency situations.

I think the poster wants to try one out, just as shown in this video about Aircraft Life Vest Full Detailed Demonstration. But yes, @TerranSwett, the title is ambiguous.

If you want one, try eBay - there are plenty available.

You can buy aircraft life vests pretty inexpensively for the purpose of having one or seeing how they work.
There are a bunch of used ones for sale on eBay, they may have been taken from planes over the years or they may just find their way into circulation after being removed (before being trashed).
Some of them get upcycled/recycled into other things so they presumably enter circulation at some point.

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Can a cyclogyro autorotate in an engine-out emergency?
A plane without a propeller is a glider.
A helicopter without it's engine can also glide. It's like a falling maple seed, except that a significant forward velocity is needed to keep the descent rate safe.
What about a cyclogyro? This kind of craft tilts it's propeller sideways. It employs cyclic pitch control using a swash plate of sorts. Such a design has noise and maneuverability advantages. If the engine is lost but control is maintained, can it glide to a soft landing?
I would think so given that it could turn into a vertical wind turbine and keep itself spinning. As long as the pilot reacted appropriately. But can it do so in a way that preserves gliding lift?

"A plane without a propeller is a glider."   Hmmm... I may have more glider time than I realized!

@RalphJ what do you fly

@RalphJ let me guess: Jet Pilot? :)

@kruemi Which are apparently also considered gliders now! (See comments on this answer for substantiation.)

Hm, jetliners these days are propeller craft in disguise: The bulk of the thrust coming from the fan pushing bypass air instead of the hot exhaust gasses.

In short
A cyclogyro, like this example from Wikipedia:

can perform an autorotated descent with engines out, according to theory and tests made on models by Carl Bruno Strandgren, one of the pioneers in the domain, and apparently the first one to file a patent for a feathering paddle wheel in 1933.

Details
Strandgren, a swedish inventor who also invented the roller screw, researched a rotating wing for several years, which he presented in a French publication in 1933.
The article was translated and presented before NACA in November 1933:

This report provides a description of the Standgren flying machine which consists of two wheels with a certain number of equidistant blades arranged around the horizontal axis of rotation and parallel to this axis. Each blade is fixed so as to be able to feather about an axis parallel to its span at the same time as it turns about the general axis of rotation.

The author explains, by calculation and experimentation on models at the Institut Aérotechnique de Saint-Cyr, the aircraft allows autorotation at any descent angle, including vertically, when properly controlled.

A system of controls permits feathering or change of incidence of the blades to conform to the desired effect: hovering, lift and propulsion combined, gliding descent, vertical descent in autorotation, etc. (Source: NACA.)

Descent with engine stopped should not present any difficulty - no more than landing - which can be effected at any inclination, including the vertical. (Source: NACA.)

A full scale aircraft was then built by Lioré & Olivier:

(Source: NACA)
The idea led to more patents (e.g. from Platt and Laskowitz) and tests at MIT and at Langley field, but it was not developed further until recent years.
A modern study, in 2009, Review of Historic and Modern Cyclogyro Design, stated:

The cycloidal rotor has mathematically and experimentally been deemed capable of autorotation. This phenomenon is very important to the safety of helicopter flight, and may help to ensure the safety of cyclogyro flight.


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Rotor-wing aircraft feasibility
Could an aircraft have a spinning wing as a helicopter rotor at low speeds which stops spinning at high speeds to act like an airplane wing? The tail-rotor would turn 90 degrees and become a pusher propeller when this happens.
This is different than tilt-rotors or tilt-wings because in my case the rotors/wing switches from vertical thrust to vertical lift instead of switching from vertical thrust to horizontal thrust.
There must be some serious flaw with my design, and stopping the rotor fast enough to avoid retreating blade stall may be a problem. Maybe we could set the collective to almost zero and have a short period of low-g while we transform (but not negative g which would be bad)?
Helicopter blades have shorter chord than airplane wings which may force us to get a not-so-good compromise.

Is this design going to have an aerofoil moving backward at some point? Unsure if there is an wing form that works efficiently with reversed flow.

I invite you to investigate the Sikorsky X2 before you consider this further.

@KorvinStarmast what exactly do you mean by that? Because of alternate loading of the wing blades or because you think that the coaxial main-rotor with pusher propeller configuration is superior?

@U_flow Because they demonstrated how to make it work, and  because it doesn't include the rube goldberg feature of trying to change the tail rotor in to a thrust producing feature. The tail-rotor would turn 90 degrees and become a pusher propeller when this happens This is a great idea if you want to kill people, but not if you want to design a new generation of rotary wing aircraft. The 'stacked" blade discs have been around for a while, to include the Russian Hormone/Helix aircraft, and now the X2, S-97, and Defiant. Granted, they are still works in progress. (I do not work for SAC).

Yes that is possible and also has been demonstrated a couple of times:

The concept is a special case of a convertiplane, sometimes called a stoprotor or Heliplane. Sikorsky tried to demonstrate it, even an X-Plane, the X-50 was built for demonstration purposes. However none of these full-size demonstrators sucessfully transitioned to forward flight. The X-50 was even cancelled, because both demonstrators crashed. Nowadays there are UAV concepts which have a similar concepts in mind.
The problems you mention do exist, unfortunately I could not find a reference how exactly the demonstrators solved all these problems. From what I can see: One of the wings will be experiencing reverse flow, it looks like the Sikorsky simply used very thick wings to overcome this problem.
However retreating blade stall is not an issue, simply because by stopping the rotor you get less retreating blade stall.
I have not (yet?) seen your concept that the tail rotor swivels in order to create forward thrust. But I think that is not essential for the grander idea of stopping the rotor in mid-flight in order for it to act like a wing.

"However retreating blade stall is not an issue, simply because by stopping the rotor you get less retreating blade stall." Maybe I should phrase it as "retreating blade transient loss of lift" since the airfoil does not necessarily stall as the zero airspeed point passes through it.

You will get a transient in Lift, meaning that in Rotorcraft flight mode, retreating blade stall will be experienced at the retreating blades while more lift is experienced at the advancing blades. When you stop the rotor, this unbalance of lift will diminish until the rotor is stopped and normal flight is achieved.


text:
Why is the ratio of TSFC at altitude vs. sea level different for hi-bypass vs. lo-bypass turbofan engines?
I've read up on how the thrust-specific fuel consumption of turbofan/turbine engines increases with altitude, and the Georgia Institute of Technology plot in particular seems to indicate that, for most modern airliners, the TSFC at cruise is 1.6 to 1.7 that of static thrust at sea level.
Now, I've come across this site (courtesy of the Wikipedia page for TSFC) and noted some wide variations with $TSFC_{cruise}$ vs. $TSFC_{0}$.
Some examples (data from the page linked above):

GE CF6-50C2: $\dfrac{TSFC_{cruise}}{TSFC_{0}} = \dfrac{0.630}{0.371} = 1.698$.
P&W PW2040: $\dfrac{0.582}{0.330} = 1.764$.
RR RB.211-535E4-37: $\dfrac{0.598}{0.324} = 1.846$.
P&W JT8D-15A: $\dfrac{0.810}{0.590} = 1.373$.
RR Conway RCo.12 Mk.508: $\dfrac{0.822}{0.726} = 1.132$.
RR Spey RSp.4 Mk.511-5: $\dfrac{0.770}{0.600} = 1.283$.

The upper three examples are high-bypass turbofans, and the lower three are low-bypass.  Notice the big differences in the TSFC ratios.
What causes this difference?

You would have to check at what altitude "cruise" is.  When the B-52 was originally designed to fly at high altitudes, the lower bypass engines may have been better.  Your data shows the fans giving better TSFC cruise even though they have higher ratios.  No surprise they do better at lower Mach/denser air, where props once ruled.

The factor affecting TSFC is speed, not altitude. Altitude is indirectly responsible because the lower density requires a higher flight speed.
Low-bypass engines have a higher exit speed, so the change in speed affects their efficiency less. High-bypass engines double their TSFC between static and Mach 0.8 and only the lower temperature at altitude reduces the difference a bit. If you look at the formula for thermal efficiency in this answer, you see that efficiency drops more over speed for high-bypass engines. Only the much better propulsive efficiency of high-bypass engines makes them overall better for airliners.

Thank you kind sir... I find it interesting how the engineering benefits of high-bypass turbofans are somewhat diminished at cruise altitudes compared to their small-fan ancestry.

@JanHudec Of course. I even linked to the respective answer. Please note the only the lower temperature at altitude reduces the difference a bit part of the answer.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Why such a small Krueger flap on 777-300?
Why is there such a small Krueger flap just inboard of the engine pylon on the Boeing 777-300, when the rest of the wing (including the further-inboard section of the wing) has leading edge slats?
I don't see an equivalent Krueger flap outboard of the pylon, unless there is one but can't be seen in this video There isn't a Krueger flap outboard of the pylon, according to this image from Wikipedia.
Refer to this video (flap extension beginning at 2:35).

Screenshot from the linked video with Krueger flap circled.

Notice how the fully-extended Krueger flap sits lower than the neighboring slats.  Here's another video example: https://youtu.be/RbZTYP0kGbE?si=dpsfDDHZG6cTty3u&t=937

Due to wing sweep the engine nacelle blocks airflow that would feed a slot in that location, so the Kreuger flap is used instead. Outboard the pylon there is no such problem.

ref


text:
What is the purpose of this loop in a taxiway?
This image is of Mariscal Sucre International Airport near Quito, Ecuador.  (Official site / in English)
What is the purpose of the loop in the taxiway plainly visible in this image?

From Google Earth (with the contrast punched up a bit)
Addendum
To respond to the comments to jwzumwalt's answer, I really don't think the hills and mountains to the north of this airport are an operational concern.  See below image:

Source plus my copy-and-paste extras
The airport's elevation is 7900 feet (verified by Skyvector), the first ridge in jwzumwalt's 2nd image is 6.4 miles distant from the north end of the runway and lower in elevation, and the second ridge is 8 miles distant but only 500 feet higher.  Distances verified by Google Maps.
If an aircraft can't comfortably clear a ridge 500 ft above the airfield in eight miles, well then that's a whole other issue. :-)
But, I do like jwzumwalt's answer.  Thanks!

After seeing your data, I admit the Google map was deceiving me. However, the peak just to the right of your "8,432" is "9167 ft". That's a difference of 1270ft + obstructions (if it has towers might be ~2500ft). At that altitude on a hot humid day many aircraft would not be able to climb above. At 25C (77F) a C-172 has 200fpm climb which coincidentally at 80mph/~120fps a C-172 will climb 200ft per mile and wouldn't clear tall obstructions along it's path.

I sent the following message to the airport using their website: I'm hoping you can provide a definitive answer to the question on aviation.stackexchange.com concerning the use of the loop in the taxiway at the north end of the runway off the west side. The url to see the question and guesses so far is https://aviation.stackexchange.com/questions/52663/what-is-the-purpose-of-this-loop-in-a-taxiway. My guess is that it is to facilitate aircraft movement when using rwy 18 for takeoff and 36 for arrival.

In the US, this is called a "run up area". It is used by small piston powered airplanes to test their engine prior to takeoff.
The circular design allows several aircraft to full throttle their engines without the prop blast hitting the aircraft behind it. It also allows other aircraft like a business jet, to pass the testing aircraft and takeoff immediately.
Larger aircraft or turbine powered aircraft don't usually test their engines near taxi-ways and other aircraft (or aren't allowed). If they need to test their engines, a special blast "pen" or blast "barrier" is used.

Youtube video of a FedEx engine test.

This Youtube video of a airplane landing shows a ground view of the significance of the hills and mountains off the departure end of 36.

Why the run-up is at this end - Google Earth 3D

Thank you for the answer, but I'm still curious, how come this run-up area is at the opposite end of the take-off runway usually used at UIO?  Or is that the normal procedure / location?  (I don't have wind rose data, but suffice it to say that at UIO, nearly always T/O and landings are to the north.)

Aircraft use either end of a runway depending on wind direction. The Mariscal Sucre runway has high speed exits in both directions showing it is used in both directions. However, due to hills to the North, it appears landings are normally from the South and takeoffs are from the North end.

@jwzumwalt: Umm, every time I've been to that airport, day or night, all operations are on Runway 36.  As for the hills, well check out https://youtu.be/7G0lTmezE_Q.  Disclosure: I recorded that video.

@pr1268 You're correct on that, the Ecuadorean AIP says that 36 is used for all takeoffs and landings, except when the wind is from the south at 8kts or more, then 18 can be used. 36 departures may not turn right, and 18 departures may not turn left, so I guess the terrain east of the airport is the main operational issue. There's nothing specific that I can see in the AIP about taxiway T, by the way.

Here's the exception to the rule:  A landing on Runway 18. https://youtu.be/qCVmDIT4qEA

Also looking at the layout of the airport, it gives planes a holding area in case they need more time to get ready. If there was traffic behind them they would have to taxi down the runway until the mid-point and then back up the taxiway

Quito is a high airport with some long haul flights.. take-off performance may be restricted and this may result in the plane being a bit overweight so this may be an area to allow for airplanes to burn-off some fuel.
As an example the aircraft may have a restricted take-off weight of 280,000kgs. A forecast ZFW (weight without fuel or zero fuel weight) of 200,000kgs may be given to the crew. The crew may then decide to uplift 80,000kgs of fuel which would bring the take-off weight up to the allowed 280,000kgs. However as the forecast ZFW was only a forecast.. the actual ZFW may exceed due to last-minute passengers, cargo, baggage etc. If it is a big amount (more than 2-3000kgs) they would probably offload some cargo but if it was only 1,000kgs or so the crew may elect to burn off some fuel to get the legal weight before taking off.


text:
Can two aircraft be allowed to stay on the same tower-controlled runway at the same time?
My understanding is that a runway at a tower-controlled airport should always be cleared, and occupied by no more than a single aircraft for takeoff and/or landing at any given time.
Is there any scenario in which ATC can clear two aircraft to occupy the same runway at the same time? Like clearing them to takeoff one by one: clear the front one to use part of the runway to takeoff first, and then clear the other at the threshold to takeoff.

Does the FAA have an equivalent of the CAA 'land after' clearance?

@Dave, as I understand the "land after" clearance: Yes, the FAA has it, and it's called anticipating separation. Technically ATC is supposed to issue traffic but in reality that often gets dropped, especially if all aircraft involved are landing (none departing). It's very common to have two or three or even four aircraft all on the Tower frequency and all cleared to land on the same runway, and the only thing Tower has said to each one is "cleared to land."

Yes, it is possible, under some circumstances. However, your general understanding that only one aircraft is allowed on a runway at one time is correct most of the time.
There are a few obvious cases, also covered in the other answers. For instance, an aircraft can be allowed to cross or taxi on a runway behind another aircraft which is taking off or landing. An aircraft waiting to depart can also be cleared to enter/line up on a runway behind another aircraft taking off or landing. These examples are pretty simple, because only one aircraft is actually using the runway for takeoff or landing, the other is just taxiing behind. But actually, two aircraft can takeoff or land on the same runway at the same time in accordance with the below, and as stated in ICAO Doc 4444 section 7.10 on Reduced Runway Separation.

An aircraft can land on a runway while another aircraft in front of it is also landing, provided that the first aircraft has touched down, is in motion and will vacate the runway without backtracking (doing a 180 on the runway).
An aircraft can land on a runway while another aircraft in front of it is taking off from that runway, provided that the first aircraft is airborne.
An aircraft can take off from a runway while another aircraft in front of it is also taking off, provided that the first aircraft is airborne (but still over the runway, and thus not clear of the runway yet).

ICAO suggests some pretty strict requirements in order to use these rules, such as the exact distance needed between the aircraft involved, as well as the type of aircraft, runway length etc. However, some states have pretty lenient rules. In Denmark, for example, it is largely up to the air traffic controller on duty to decide if conditions are safe to use reduced runway separation. The phraseology used is a little different as well:

Instead of the usual "cleared to land", the phraseology used is "Land behind preceding landing (aircraft type)". The second aircraft will obviously have been informed of the first one, and weather conditions must permit the pilot to see the first aircraft at all times.
Similar to 1, the phraseology is "Land behind preceding departing (aircraft type)".
A normal "cleared for takeoff" is used, but the pilot of the second aircraft must have been informed of the preceding aircraft and have it visually in sight.

There is another scenario other than "line up and wait" that the other two answers cover...
A "flight" of more than one aircraft may be cleared as a group to take-off. This can consist of many aircraft sharing the runway during take-off (and even landing).
So you can have multiple aircraft on the runway when:

A "line up and wait" order is issued to line up on the runway after another aircraft takes-off or lands. This is usually done so that the departing aircraft can get prepared while waiting for wake-turbulence to clear.
ATC clears multiple aircraft as a "flight". The aircraft must be part of a coordinated group and a single aircraft is the "lead" aircraft for the flight that receives/coordinates with ATC for clearances. The entire flight group will enter the runway and take off in a pre-coordinated fashion.

There are specialized scenarios as well, for example during Airventure Oshkosh. Aircraft will be required to "land on the dot" and multiple aircraft may be on the runway for take-off at the same time, although ATC coordinates them so that they don't depart at the same time, they are asked to line up "on a dot" (a colored circle on the runway) and will then be cleared to depart from there.
As an extreme example:

116 aircraft lined up on the runway and cleared for take-off at the same time.

How did this get signed off?!

@Cloud Because they were extremely well-coordinated. ATC probably knew months in advance that they were coming and what time they wanted to depart, down to the minute. They had pre-flight meetings with the pilots and if you notice, the pilots had color-coordinated cards for every scenario. They also coordinated with Airventure tower in advance to be able to receive that many aircraft at a specific time. I'm sure they knew before they even took off that they would be cleared through the FISK arrival.

These are also very small planes that presumably don't need very much runway to take off.  If this runway is designed for 747's, there's more than enough space to line them all up with room for take offs.

Nine aircraft synchronised take off: https://m.youtube.com/watch?v=mtNc8ZXuHVI

6:35 "Traffic, twelve o'clock, same altitude, zero miles."

Why is one of the pilots wearing what appears to be a golf glove? (3:53 in the embedded video)

Historically, scrambling military aircraft would involve several planes taking off simultaneously in formation, so this guaranteed more than one aircraft on the runway at once.  In addition, the next formation to take off was generally lined up and ready to go behind them.  For interception duties, this enabled as many planes as possible to take off in as short a time as possible, giving the pilots an invaluable few extra minutes to gain height in preparation.  This can be clearly seen in this Pathe footage, where Spitfires and Hurricanes launch in formations of three aircraft.
Strategic bombers adopted (and still use) a similar technique called minimum takeoff interval, designed to get nuclear bombers airborne as rapidly as possible for a retaliatory counterstrike in the event of attack by nuclear missiles.  With the high turbulence from preceding aircraft, takeoff does become very much more risky, but it remains standard practise.
Having more than one aircraft on the runway at once is therefore entirely familiar for military ATC.

This is standard operating procedure for towplane-glider takeoff.
Clearance with ATC is covered by 14 CFR § 91.309

Multiple aircraft (i.e. the towplane + the glider) on the runway at the same time is standard ops when launching gliders this way. The question asks about “multiple aircraft”, not “multiple flights.” Seems adequately clear to me.

This is an unexpected but valid answer to a fuzzy question.

@ymb1 Launching gliders with an aero-tow is an example of what the OP asked about: if/when you can have 2 aircraft on the runway at once. It's a clear, responsive answer to the original question.

I've seen this often in Atlanta. An aircraft will start its takeoff roll, with the next aircraft behind the line. Once rolling aircraft is about halfway down the runway, the next aircraft will slowly start to move onto the runway.
If you're on board on the side you'll be taking off on, you can typically watch the preceding aircraft as it reaches V1 and rotates, just before your aircraft finishes its turn to line up with the runway.

Likewise with a landing aircraft, the following departure may "position and hold" while the landing aircraft completes its landing rollout, so the following craft can depart as soon as the previous one clears the runway.

@GalacticCowboy "Position and Hold" is outdated, the recommend phrasology is "Line up and wait": https://www.faa.gov/airports/runway_safety/news/current_events/lauw/

@Tyzoid The concept is still the same.

@GalacticCowboy your point is valid. However, we do try to keep things as current as possible to avoid confusion for people who may come read this in the future. No sense educating someone on the old phraseology that will cause confusion if they were to actually use it. *Yes, a pilot should be trained on current standards, however, some things will stick in your head and are hard to get out....

It's a great point that in these cases, you can actually see the previous craft taking off!  ATL (the world's busiest airport, I believe) is the prime example.

If a runway has multiple crossing taxiways then ground control can clear several aircraft to cross the runway at the same time.
If a runway is not being used for landings or takeoffs (in favor of another runway) then it can be used like any other taxiway (other than the clearance and read-back requirements). On busy airports during peak hours this could mean the runway can be use as a holding point for aircraft waiting for their gate to become available.


text:
Does the A320's FMC automatically adjust the rate of descent on a non-precision approach?
Does the A320's FMC automatically adjust the rate of descent on a non-precision approach? Like a back course approach for example if the distance to altitude is (or can be) programmed in?


text:
What angle of deflection / pitch on the rotor blades can the controls generate?
I was wondering, if a pilot uses full input on cyclic and collective, what pitch angle can be achieved for the rotor blades? Is there a mechanical stop to prevent extreme angles of attack? And how would that interact with the blade pitch needed for auto-rotation?
Thanks!

Maximum pitch angle would totally depend on the type of helicopter you are flying. Each helicopter has its own set of limitations and pitch angles depending on the blade, rpm, etc. The controls include a mechanical stop, and you would hit that limit sooner or later if you put in an overly aggressive control input on the cyclic, or full collective up or down. Think of it as the same way you would hit the outside edge of the control on a video game joystick.
In "real life", the pitch angle numbers are irrelevant to a helicopter pilot. During
autorotation, the RPM of the spinning blades is maintained by reducing the pitch angle allowing an upflow of air from the descent to maintain the rotors spinning - similar to blowing air on a fan in order to keep the fan blades moving. The rotor RPM can be adjusted through up and down collective movements, which will in turn increase or reduce the RPM required.

Thank you for the answer! What I meant was specifically the deflection of the pitch angle from its neutral position. How many degrees about the feathering axis of the blade can the pitch links induce. It's more about the mechanics of the rotor hub/controls, not the piloting experience side of things. I don't think it would matter whether the engine is on or off for that, or the current RPM.

On the Robinson R44 for example (Robinson publishes their maintenance manual so you can reference section 10.122, Page 10.11), full collective down pitch 1-2 degrees down, 11.5-12.5 degrees up.

Perfect! Thank you!

Each control (collective, longitudinal cyclic, and lateral cyclic) can provide a specific range of blade root pitch.  E.g. the collective may pitch the blade a total of 20 degrees from minimum to maximum position.
The angle of attack (AOA) depends on the flight condition.  The same "control blade angle" will result in a different AOA in descent compared to climb.  There is no mechanism to explicitly limit this AOA.
Notice above I said the pitch angle range only!  The physical pitch angles depend on helicopter-specific mechanical settings.  E.g. if a helicopter will be flown in a region of very high air density the maintainer will adjust that 20 degree collective range to be at smaller blade angles (say -3deg to +17deg instead of 0deg to +20deg).  See this link for more details.


text:
Can a civilian helicopter regularly fly low & close to houses?
There is a helicopter which regularly (1 to 5Xs a month) at night or day flies very low & fast, has flown over a vehicle, playing a chasing game down neighbor's driveway and down the road. Who can I report this to as it also has spooked pets and wildlife?

Which country and city is this? Any possible advice would need that information I think.

What do you mean by "playing a chasing game down a neighbor's driveway and down the road"? Are you talking about a remote-controlled helicopter, or a full-sized one?

You have no location information in your post or user profile. Obviously the answer depends on country.

The question as it stands now is asking one thing in the headline, and the other in the body. I'll answer the latter.
In any case of public disturbance your first point of contact is the police. If the disturbance is acute, you may call emergency number (depending on your location  911, 112 or something else).
You may also find out what is the aviation authority in your country, and contact them.
For both, I bet finding contact information by google takes less than a minute, so it will be quicker that writing this answer was.

Assuming this happened in the US-- harassing wildlife can be a serious offence on various levels (state, federal, etc) even if no specific FAA regulation has been violated.  At least if you can show the pilot knew or should have known that wildlife was being harassed.


text:
Why do all fifth generation fighters (J20, F22, SU57) put their wing above the fuselage?
I heard that upper wing could increase stability, but why do fighters need it? Or are there some other reasons? Please specify.

One big reason is to make room for external stores such as fuel, weapons and electronics packs. A low-wing design must have longer and therefore heavier and bulkier undercarriage if ground access to the underwing hard points is to be adequate.
Also, the upper surface of a high wing is larger and cleaner, providing better lift over the fuselage and reducing the overall size of the wing.
Another trick which it allows is to create a waverider effect between the engines, providing supersonic lift with less drag.
The extra stability of the high wing position is unwelcome in a fighter and is typically countered by giving the wings a little anhedral, a slight downwards slope from root to tip.

I would not place ground clearance of external loads very high on this list, because use of external hardpoints totally destroys the stealthiness of these fighters. For delivery of large amounts of destructive payload there are far more cheaper and effective methods than 5th gen. fighters. It is kind of funny they are equipped with such capability.

Agreed, there are low-wing airplanes with internal weapons stores. The F-117 for example.

@Jpe61, in case you haven't noticed, combat between modern forces is rather rare these days.  An airplane that can drop a large load of unpleasantness on an opponent that's still equipped with WWII-vintage hardware is far more useful than one that can only be stored in a climate-controlled hangar on the off-chance that WWIII breaks out.

Your point is what @Mark ? Gen.4 fighters will be used for decades. They are the ones delivering the mass punch. Gen.5 has a whole different strategic role.


text:
Are any online resources available for ATC recordings?
liveatc.net is available, but the voice quality on there, I am given to understand, does not represent the quality of voice available to someone actually sitting in an ATC tower. So I am looking for a source which offers more representative recordings.
EDIT: I intend to use these recordings to evaluate which speech to text engine (Non comprehensive list) works best in the context of aviation, so recordings which best mirror what happens in reality are important to reduce pre-processing.

Go for a plane ride and listen to the sound quality...  liveatc.net is pretty spot on!  :D

If you would explain what you need these recordings for, it would be easier to come up with a useful answer.

Are you interested in Tower communication first (approach, landing, T/O, departure)? Tower exchange will usually be more clear than another communication, as aircraft are closer. On the other hand, archiving audio streams takes storage resources, I doubt the sampling of the archive will be better than what is transmitted once using multicast.

I I hope the edit clarifies things, i'm hoping there's something out there on the basis of the replies to this

If you want to teach a speech-to-text engine you should use bad quality recordings instead of good ones. More often then not the quality of the radio transmissions is not very good. The human brain can "fill in the gaps" but a software program does not have the intelligence to do that. Using bad recordings will at least teach it to filter out the static a little bit more.

@RonBeyer: Just for sharing... Face Recognition Algorithms Surpass Humans. I believe this is the same for speech recognition, but I've no study at hand. Algorithms are actually able to cope with incomplete information if they are trained. The so-called "big data" raw material will be mostly live video, audio, and other unstructured data found in live data streams that won't be stored at all, only used.

@mins Don't want to turn this into a discussion but I work with SR quite a bit, and SR is significantly more complicated than facial recognition. The biggest issues are things like inflection, pronunciation, accents, etc. Add in the different frequencies and volumes of voices along with noise and the issue is compounded. Facial recognition is easy, a face is a face, but the same word can sound very different depending on who speaks it. There is also no context in FR, where context plays a big part in SR to fill in the gaps.

LiveATC is probably your best shot. The quality you'll get on the stream depends on where the receiver is setup. Since aircraft communications are in VHF or UHF (military) reception is basically within line-of-sight range. This is why often you'll hear the aircraft side of the conversation without hearing ATC.
I would just browse the various streams on LiveATC until you find a good one. OR, if you're near an airport, set up your own receiver!

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
How much weight does removing a vacuum system really save?
For a small GA aircraft (e.g. Piper, Cessna, Mooney), does anyone have a before and after weight savings example from removing a vacuum system?  E.g. calculated weight of component removal during W&B?
The context is replacing a standby attitude indicator with an electronic standby (e.g. MidContinent, Sandia SAI 340, etc)..
This question specifically refers to the vacuum system only, not the instruments themselves.  E.g. vacuum pump, hoses, fittings, etc.  Thanks!!

Why would you want to do that?

See Relevant Past Practice for a brief overview of the "why":  http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgPolicy.nsf/0/6a24902ae5f1aeac86257ec1005b2fbc/$FILE/PS-ACE-23-08.pdf

I removed the vacuum system in my VariEze a couple of years ago and saved 12 lb including the artificial horizon and heading indicator.  Probably about half of that was the instruments, the rest being in the pump/hose/regulator/filter/fittings.


text:
Checklists before take off - how often must they be performed?
Friday I was on a plane from MXP to Prague, should have been a 737-400, and the take off was preceded by something I'm not sure what it was: probably a pre-flight checklist, but it's the first time I see something like this:

The plane got pushed back by a tractor from ramps to apron - at least, I think it was the apron- and turned (still by the tractor) in the right direction for the taxiway
Engines thrust was increased and decreased a few times, keeping them at "high" levels for a bit
Control surfaces were checked as usual

I'm used to pilots checking control's surfaces either while still at ramps or on the taxiway while waiting for their turn to take off, or just at the beginning of the runway, but never seen anything different and never seen "testing" the engines that way, and it got me wondered about check list frequencies.
Was that routine some kind of checklist? And if so, is there a specific regulation about how often it must be performed? (and, by the way...I know that it's possibile to load fuel even with passenger on board, but...testing engines with plane full loaded? Isn't it a bit too dangerous?)

And to not litter the answer: if the pilot of that flight is by chance reading this...BEST-LANDING-EVER. Seriously amazing. The only description I can come off is "went from flying in the air to flying on the ground". Never ever seen that level of precision and control of the aircraft, absolutely spectacular!

Maybe some maintenance had been done and the pilot wanted to check that it had cured the symptoms of a previously reported problem?

Can be many things: 1- An engine check for any maintenance request. 2- depending on the ground softness sometimes pilots have to increase the power to get a heavy aircraft to move 3- improbably a run up check for icing but I think on Friday was still good weather in Italy. need more details, like was the aircraft static? Did the pushback truck disconnected ? This kind of test does nothing to do with checklists, normal nor emergency checklist. Sorry if I could not give you a streight answer.

@motoDrizzt In regards to your BEST-LANDING-EVER comment, remember that luck as well as skill enter in to the quality of a landing. When you do something thousands of times, even a poor pilot sometimes gets an exceptional landing and an exceptional pilot a poor landing. The condition of the runway surface as well as the aircraft type also play a significant roll.

@Terry I know, obviously, it's always a bit of this and a bit of that: luck, skills, weather...e.g. it's not pilot's fault if he has to land in a strong side wind nor he's a better pilot if he land in ideal conditions. So, as I know all of this and I never complain about a rough landing, I feel there is nothing wrong in being impressed by a good landing. It was, anyway, the best I ever experienced and being positive costs nothing :-)

For an airline crew, the Before Takeoff Checklist is performed once before every takeoff.  There is normally no "run up" associated with such a checklist for jet aircraft.
Depending on what else is going on, there are reasons that engine power might be advanced then reduced, and it would be speculation as to what the reason for that was on your particular flight.

The amount of times they do the checklist is not important.  There's things that are repeated between checklists.  For example, some aircraft have control surface checks both on the ramp and while taxiing.  Regarding the engine run-up, the pilot would not do it if it was hazardous to passengers.  Engine run-ups are usually performed somewhere between the ramp and takeoff.  Engine run-ups are a must.  Other reasons for engine run-ups could be carb cleansing (for non-fuel injection pistons), engine temperature adjustments, etc.

I'd love to accept the answer, but as it is it lacks a bit of details. As it stand, for example, it sounds like the pre-flight check list is not mandatory ("The amount of times they do the checklist is not important"), and "engine run-up" means...?

I would be very surprised to know that preflight checklist is not mandatory. please google engine run-up.

"The amount of times they do the checklist is not important." Disagree. At least once is surely required.

Engines thrust was increased and decreased a few times, keeping them
  at "high" levels for a bit

This could be as a result of a recent maintenance note on the aircraft, which resulted in some configuration changes or modifications to the engines, thrusts, throttles or any number of things in the middle.
If my memory is correct, the 737-400 is not a fly-by-wire aircraft; so there is a lot of mechanical stuff going on.
So it could be simple run up to verify things in the mechanics log.

I'm used to pilots checking control's surfaces either while still at
  ramps or on the taxiway while waiting for their turn to take off, or
  just at the beginning of the runway, but never seen anything different
  and never seen "testing" the engines that way, and it got me wondered
  about check list frequencies.

Unless some extraordinary exception is in place, control surfaces are not checked at the gate or at the ramp; simply because most of these test have to be performed post engine startup in order to ensure all systems and redundancies are tested.
If flight controls are being tested (ie, full range being tested) on the runway this is definitely not normal.

(and, by the way...I know that it's possibile to load fuel even with
  passenger on board, but...testing engines with plane full loaded?
  Isn't it a bit too dangerous?)

Most commercial airplanes can be fueled with the engines running (but at idle), but for safety reasons, it is almost never done.
Having passengers on board during refueling happens quite often. You'll know its going on because the crew will inform passengers to be seated.
Regarding your main question about checklists - they must be performed once at the respected stage of flight. So a taxi checklist is done before each taxi, takeoff before each takeoff and so on.

I don't quite understand your response to the third quoted section of the question. The asker clearly states that they know it's OK to fuel with passengers on board but the question is about testing engines with passengers on board. Your response just reiterates that it's OK to fuel with passengers on board and says nothing about testing engines, which is the only thing being asked about.


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Is it reasonable for flight economy to correct banking tendencies with stick and rudder?
An aircraft with side-by-side seating but only one person aboard should fly banked.  Banking decreases lift and more elevator is needed than in leveled flight which increases drag. Correcting the banking with ailerons and rudder also increase drag. Which is better for economy?

You might be better off correcting weight imbalance with more fuel in the opposite wing if possible.  Then fly with fuel selector on both as long as you can.  This should give you better economy than trimming aerodynamicly.
Notice this also true for weight too far forward or aft.  Good balance helps in the air.

Based on your question, you are correct:  It will take more fuel to fly at a constant angle of bank.
If your goal is to remain at a constant altitude for as long as possible it would be better to fly straight and level, properly trimmed with the ball centered, than to orbit in a circle at a constant angle of bank with the additional elevator trim required to maintain altitude.

You are really describing a banking tendency no?  If the airplane is banked, it will turn.  To make it fly with bank, without turning, you have to use opposite rudder, creating a sideslip, which you would never do.
So if you have a banking tendency, that is the airplane wants to roll in a certain direction all the time, is the banking tendency happening while the airplane is flying straight (ball centered) or is the banking tendency because the airplane is skidding (ball offset).
If you center the ball with rudder, so the tail is lined up behind the nose, and the airplane still wants to bank if you let go of the ailerons, you have either an unequal lift problem (something in the wings is not symmetrical) or a lateral weight distribution problem.
The options are to hold aileron input, with the ailerons displaced from neutral, to counteract the rolling tendency, or counteract the rolling tendency with lateral weight offset that results in the airplane flying level with ball centered with no aileron displacement.
From an efficiency standpoint, you want to avoid flying with controls displaced into the airstream, so it's more efficient to use weight offset to counteract a rolling tendency if offset is able to achieve wings level without displacing the ailerons.  On a lot of airplanes you can achieve this with lateral fuel differentials when it's possible to feed from one tank or the other.  You can create a deliberate fuel imbalance that counteracts the rolling tendency, then maintain this imbalance by switching back and forth as fuel is burned.  I do this in my plane because it is quite sensitive to lateral balance.

The original question was how to balance a single occupant‘s rolling moment in a light aircraft (i.e. lateral imbalance), if I understood correctly.

Yes, that was exactly my original question. Leveling the slight banking needs only a slight touch in stick that can be tolerated but the constant left rudder (without a rudder trim) is inconvenient for the pilot. So I wondered how uneconomical is it to fly slightly banked and control the direction only with stick.

Well the answer is buried in my blah blah blah. Don't use rudder to stop a rolling/turning tendency if the rudder application sends the skid ball off center.  Only use rudder to center the ball.  If it wants to bank with the ball centered, either hold the aileron in or shift fuel to make it go away.  Otherwise you are flying along cockeyed.

You did not answer my question. The ball will be centered with aileron and rudder. But the question is economy: is it significantly uneconomical to fly slightly banked, elevator trimmed, direction controlled with stick and.. of course.. the ball slightly on the left due to banking. Forget the fuel.

If I understand your question, it is that having a single occupant aboard offsets the CG from the longitudinal axis of the aircraft causing a slight roll of the aircraft until the CG again aligns itself along the longitudinal axis.
This is, at least technically correct.  However in most aircraft design features such as pendulum effect, preset trim tabs and dihedral angle of the wings largely diminish this to the point of being imperceptible to the pilot.  You won’t even notice a difference flying solo as opposed to an even number of passengers aboard.
Whatever effects associated with this are nothing compared to the effects of overbwnking tendencies, left turning tendancies eg P-Factor, torque, spiral slipstream and propeller gyroscopic precession, thrust asymmetry from an inoperative engine(s), etc.  these maladies are usually corrected by means of trim on larger aircraft or dampened out by flight control computers.
So yes, to be sure, the asymmetric loading from a single pilot does try to roll the aircraft slightly, which has to be countered with a roll torque opposing it which has additional aerodynamic consequences associated with it.   It it’s so minor and countered by inherent design features for positive static and dynamic stability that you won’t even notice the difference in flight.

With single pilot the lateral weight imbalance induces slight banking, so slight that turning tendency is minimal and almost unnoticable. But if I correct the banking with ailerons, I also need slightly but constantly to use the left rudder which is inconvenient in a long flight without a rudder trim. So my question, is the extra effort to make her fly wings leveled reasonable for economical point of view or do I let her fly slightly banked which is more convenient for the pilot. (Of course the best option would be to balance the plane).

Yesterday I made an unofficial experiment with my ski plane. If the slight banking due to  solo flying was corrected with aileron and rudder, the ground speed seemed repeatedly to decrease 1-2 knots compared to letting the plane fly banked, half the ball on the left, keeping the altitude with stick -- and so apparently with better economy.

Interesting experiment, thanks for sharing!  I remember from multi engine training that it is similarly more efficient to fly with the ball just a little out of center, but I can't remember the justification well enough to repeat it.  I'm sure it has the same basis.


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Where is the weather data for the Garmin G1000 retrieved from?
In a few videos I saw the possibility of looking for example at wind data. Now my question would be where does the G1000 gets the data from?

Garmin Flight Data Services (GFDS) or Flight Information System-Broadcast (FIS-B), looks like?

That is coming from a satellite based XM weather service which provides a variety of weather products on demand to pilots using a G1000 system.


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What is the maximum angle between an airplane and runway centerline when touching down at a crab angle in a crosswind landing?
What is the maximum angle between the airplane's heading to the runway when an airplane is being landing sideway due to crosswind?

The exact angle is not what the performance specifications state. Instead, the maximum crosswind component (What is the maximum crosswind component for large airliners?) is specified, from which you can roughly work out the angle for a specific type of aircraft if you're interested. Each aircraft model is different.

90 degrees, if the crosswind's strong enough :-)

I don't think 90 degree will be possible as with angle, both rear landing gears will be parallel to the runway. With that position, the force will be strong enough to damage it.

A B777 (as in your photo) would generally have a maximum crab angle of about 16 degrees when approaching and landing at the Maximum Demonstrated Crosswind Component of 38 knots.
A 38 knot crosswind is not limiting and can be exceeded provided you apply a sideslip or crab correction at touchdown. It is however limiting if you plan to touchdown maintaining the crab.
E6B Heading, Ground Speed, And Wind Correction Angle

By using a sideslip or crab correction at touchdown, Airliners will sometimes approach and land when the wind exceeds the Maximum Demonstrated Crosswind Component. If the crosswind component was 50 knots and the aircraft was had a lower approach speed (due to light weight), the crab angle during approach could be as much as 25 degrees.

Thank you for your answer. Very informative.

What is that "calculator"? Is that available in cockpit during flight?

The E6B is type of circular slide rule which all pilots learn to use while in basic training. Very few airline pilots use them as modern airliners have Flight Management Computers that make the E6B mostly redundant.

There isn't a maximum crab angle (you aren't supposed to touch down crabbed to the extent you can prevent it) and there usually isn't a maximum crosswind component either on most airplanes as a "legal" limitation.
Usually the aircraft's AFM limitations give a maximum crosswind component (a lateral vector derived from wind direction and speed you get from using a chart) with a statement that it is the maximum "demonstrated" component and is not considered limiting.  It's simply the maximum component that was able to be tested during cert testing.
For crosswind components beyond that, it's not "illegal" to land from an exceeding aircraft limitations standpoint, but airlines may designate the demonstrated maximum component from the AFM as a hard limit for crews to observe as a policy.

As far as I can tell, the landing technique for most airliners these days is to keep the crab all the way to touch down and only add rudder to correct it once the mains are on the ground—see also Terry's comment on the other answer; unlike me he speaks from personal experience.

That is brutal on landing gears.  With really large airplanes with a lot of mass and inertia, you will see a technique of holding a wings level crab into the flare, then aligning the airplane with rudder just before touchdown. With all the mass you have a few seconds before the crosswind starts to drift you across the runway.  On smaller airplanes this doesn't work so well and it works better to land with sideslip, that is wing down with opposite rudder.  When I was flying RJs I landed in crosswinds using sideslip (couple degrees of wing down and opposite rudder), just like a light plane.

The answer varies according to the plane's design. Some planes are constructed with landing gear so robust and flexible that significant crosswinds will not overstress them during a crabbed landing (Ercoupe). Other planes are constructed with swiveling mains so the plane lands at a crab angle but the gear tracks straight down the runway (Lockheed C-5A).

The Ercoupe's trailing link gear was robust but the term stout might make ppl think it was super rigid,  It was designed to flex under side loads so it could tolerate crabbed landings.

I meant stout in the sense of "robust" i.e., it didn't break at touchdown in a crabbed attitude. Should I edit? -NN

Maybe use "stout, yet flexible" or something like that.

No airplane touches down sideways, some may approach at and angle but generally the goal is to touch down with the airframe in line with the orientation of the runway. What you see is a crabbed approach and the aircraft will straighten out prior to touching down. As Greg notes in the comments this angle is defined (and variable per aircraft) by the crosswind component. The maximum angle desired is 0 as anything above that will add side loads to the gear that are generally not a good thing. As the FAA notes in their Airplane Flying Handbook

...The crab method is executed by establishing a heading (crab) toward
  the wind with the wings level so that the airplane’s ground track
  remains aligned with the centerline of the runway. This crab angle is
  maintained until just prior to touchdown, when the longitudinal axis
  of the  airplane must be aligned with the runway to avoid sideward
  contact of the wheels with the runway.

Practically an aircraft can touch down a bit off the longitudinal axis and with proper control you can straighten it out but its generally not great for the airframe or gear. Poor longitudinal control in a tail wheel can also lead to ground looping.
The exception to this is the B52 which can actually touch down sideways although the gear is in line with the runway.

For 747s at least through the -400 series, you are allowed to touchdown in a crab up to the max demonstrated crosswind. Personally I never liked doing that and kicked out to align with the runway with a slight slip to the upwind side, but touching down in a crab was what was encouraged at the two 747-100/200 carriers I flew for; they really didn't want to drag a wing. Take a look at the copy of the Boeing Flight Crew Training Manual available at http://volarenargentina.com/descargas/_747-400_FCTM.pdf for the -400, page 6.29 for max demonstrated crosswind and 6.30 for touching down in the crab.

@Terry Interesting! You may want to add that in an answer as I did not know that and its pretty pertinent. Were side loads on the gear ever an issue in that situation.

I never heard of any side load issues, but I didn't follow maintenance concerns and history closely. I'm guessing that there wasn't any problem because it was permissible to operate with inoperative body gear steering (we did it often) which meant that every time you made taxi turn of more than just a few degrees, you were dragging the body gear sideways. Really hard on the tires.


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Electrical systems in light aircraft
How does the electrical system in a light aircraft such as a Zenith CH-750 or Cessna 150 work compared with electrical systems in larger aircraft? Are the system is different than the electrical system on a common car?  Do we need static electric discharge system?

This feels too broad to me. Asking about some aspect of the electrical system of a typical airplane of some type (say, "how is interference from static discharges prevented in a Cessna 150/152?") is almost certainly fine. Asking basically for a full description of the electrical system of "small, slow, light" aircraft (whatever exactly that means; in fairness, you do offer two specific examples which helps narrow that part down) is something that could probably require one or more books to answer properly; that makes it too broad.

"static electric discharge system" are just static wicks, having nothing to do with the electrical system except that they happen to be mounted on the same airplane.  Here's an example of one  https://www.aircraftspruce.com/catalog/elpages/esd1staticwick.php?clickkey=6974

Typically light normal category aircraft make use of either a 14 VDC or 28 VDC electrical systems powered primarily by an engine driven alternator. This provides power to one or more power bus bars which provide electrical power to the various aircraft systems requiring it.  Below is an example light aircraft electrical system from a Cessna 172S.

One notable deviation from automobile electrical systems is that the engine spark plugs receive electricity from a separate pair of magnetos which produce their power independent of the main electrical system for reasons of redundancy.

And dual spark plugs per cylinder.

Seems that there is two type voltage level in a small airplane, 12V and the 14volt. I do have to check that 14V as it it absolutely new for me. Or it just 12V plus 20% of it? Which it will give 14,4V that also common for heavy truck electrical system.

From the second drawing, I saw there written 12V. That's the only voltage indicator there. Seems the voltage is 12VDC. 12V is not 12V if we measure using voltmeter. It must be at range 12V+(12V15% - 12V20%) or 13.8V - 14.4V. Lower than that, is too low. Higher than that range can endanger the devive, especially a sensitive one.

Most light aircraft use 12vdc systems with belt driven alternators, like cars.  They generally use the same alternators and voltage regulators, sometimes identical to the auto version but just having a more stringent quality control process.
Some heavier light planes use 24vdc systems, which allows for smaller, lighter wiring, and a bit less sensitive to bad connections with the higher voltage.  More expensive to fix because the generators are dedicated aircraft units with no automotive equivalent.
For a homebuilt, you would just build a 12vdc system using automotive components, except for the battery, which has be be able to run upside down so it needs to be an aircraft one, although you could use an automotive gel cell battery.

Re "...but just having a more stringent quality control process": Or sometimes just having a higher price tag :-(

Well yes.  The story I was told long ago was that a Delco alternator on the "aircraft" production line simply went through inspections or functional tests on every unit instead of every 10th.  In the avionics industry, black boxes no longer use "milspec" electronic components like chips because they aren't manufactured any more.  It's now a "Mil Perf" (performance) standard that applies and manufacturers screen commercial hardware through a Mil Perf testing regimen and the ones that pass are considered fit for flight.

@johnk, what did you mean that the battery has to be able to run upside-down? What for? Even for non-acrobatic airplane?

Wet cell batteries have to be vented.  A normal airplane can experience 0 or negative G just from turbulence if it's bad enough, so aircraft batteries with vented cells have a check valve built into the cell caps.

@John K: And you think cars, or at least pickups driven on some of the dirt roads hereabouts, don't experience negative G?


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How can I best prepare for my first lesson on stalls?
I am a flight student preparing to practice stalls and stall recovery in a Tecnam P-2002. I have already done spin recovery. On top of that, what preparation techniques have others found useful?

While I understand why this is on hold, it would be a shame to lose the answers, as they make very good points on preparing a lesson from a student’s viewpoint. Maybe a question to roughly match the answers would be “I am a flight student preparing for a specific manoeuvre. I have already done X. On top of that, what preparation techniques have others found useful?”

Just changed the question as you said, sir. I think it would be more convenient in that. Thanks.

You will impress your instructor most by being eager to learn and learning quickly, and by having done book work beforehand.  Just do some reading on stalls and really get to know the 2002's Operating Manual, especially the numbers and limitations.
Be careful about trying to show that you already know it all.  If a student has taken the time to learn the operating manual and knows all the important numbers and limitations by heart, and can recite emergency drills etc while under stress, the instructor will way more impressed than if a student tries to show they already know how to do the lesson.  That being said, just read up, and really learn the manual.

First, the low-hanging fruit: has your instructor provided you any homework for the upcoming lesson? If so, have you done it?
I'm an instructor, and believe me, it's very easy to tell which students are doing their homework and which aren't. As John K says, doing the assigned work beforehand is a fantastic way to impress your instructor.
If there's no assigned work, you could ask for some. Unless your instructor is very new to the field, he or she probably has several resources besides the "standard" textbook that you could look at. I know here in the USA there's at minimum the FAA book, the Jeppesen book, and the Rod Machado book, and each one explains the same concept a little differently. A variety of views often helps with mastering a concept - if you don't understand a topic from one source, you might understand it with another.
Have you been chair flying? Learning numbers is good but flying is an active physical process. Find a quiet place, sit in a chair with your eyes closed, envision the cockpit, and then actually move your hands to the places that they would go during the maneuver. Taking five minutes to remember how to do it on the ground (for free) is much better than taking five minutes to remember how to do it in the air.
Are you training alone or are there others in your class? One of the best ways to learn something is to try to teach it to others. If you have classmates, try to arrange a small study group that meets regularly. Each person chooses a topic and then does their best to explain it to the group. I will warn you, it's very hard to get a group of people to agree to this, at least around here.

Very good list! I’d like to emphasize that learn your primary sources well: the POH, flight school procedures etc. And fly the chair! It is easy to focus too much on secondary actions. I’ve seen it many times that student tries to incorporate all kinds of stuff when you are there really just to learn to handle the AC. Also; doing things quickly is not same as doing them well. I’d suggest not to use PC flight simulators to learn AC handling. They are not good enough and as you haven’t done the stalls before, you’ll probably just teach yourself bad habits that are surprisingly hard to break.

I would be very careful about the study group idea. Done right, it can probably be an amazing resource; it's true that the hallmark of understanding something is being able to explain it to someone who doesn't know it. Done wrong, though, I can very easily see it resulting in people teaching each other something that is outright wrong!

Two great answers already, but I’d like to add that besides doing your homework be there on time and listen to your instructor! S/he will be telling you what you need to do.
Not many more frustrating things for an instructor than a student who is so eager to please/show off that they don’t listen to the instructions.


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Which Inlet Barrier Filter (IBF) is used in Airbus H145?
Inlet barrier filter (IBF) is an optional equipment in H145 / MBB-BK 117 / EC145 helicopters, which company Inlet Barrier Filters are used on them Donaldson, Aerometals etc..
The H145 Helionix / BK117 D2 Differences Training Course (airbus.com/content/dam/channel-specific/website-/us/training/…) mentions the Inlet Barrier Filter as an optional equipment, but The Airbus Options Catalogue for 2019 doesn't list an Inlet Barrier Filter for that aircraft.
The only IBF listed is for the AS350/H125 family

The Airbus Options Catalogue for 2019 doesn't list an Inlet Barrier Filter for that aircraft.
The only IBF listed is for the AS350/H125 family

The H145  Helionix / BK117 D2 Differences Training Course (https://www.airbus.com/content/dam/channel-specific/website-/us/training/technician-courses/h145-helionix/H145%20Differences_POI.pdf) mentions the Inlet Barrier Filter as an optional equipment.

Indeed it does, but Airbus don't list one in their optional equipment catalogue. I suggest you ask them to clarify.

Thanks CatchAsCatchCan


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What's the difference between hover power and maximum continuous power?
What's the difference between hover power and maximum continuous power? Is a pilot clear to fly when its hover power is more than maximum continuous power calculated by table?

could you post the table you are referring to, or at least the aircraft type? hover power may be a time limited power setting [like 5 min takeoff power], max continuous is the max power the engine will produce without over heating.

As the name implies, hover power is the amount of power required to hover.  If you add people/cargo to the aircraft the hover power increases.  Secondarily, it depends on air density as the rotor is more efficient in denser air - less power is required to lift the same weight.
Maximum continuous power (MCP) is the maximum power the engine/drive system should be exposed to for long periods of time.  This power level may be exceeded for shorter time periods.  For example, there may be 30 second or 2 minute power limits that are substantially higher than MCP (120%+).
I am not sure about takeoff clearances, but as you may already know power decreases substantially in forward flight and hence a helicopter that needs 1.1*MCP to lift off could still cruise around well below MCP.  Also, fuel burned in flight reduces weight and power so that less power is typically needed in the final hover/landing.  This can be upwards of a 10% reduction in weight.